Anaesthetics and peri-operative care Flashcards
What parts of a cardiovascular history are particularly important in a pre-op assessment?
Previous MI - increased risk of further infarction
Poorly controlled hypertension - risk of ishcaemic event
Heart failure - increased morbidity and mortality
Angina frequency and severity
How is an airway assessmed pre-operatively?
Is patient overweight How far can their mouth open Do they have a short neck or small mouth Is there any soft tissue swelling Any reduced flexion/extension of cervical spine Mallampati criteria Thyromental distance
What is an ASA grade 1?
Normal healthy individual without systemic disease
What is an ASA grade 2?
Person with mild to moderate systemic disease that doesn’t cause any limitation in activity eg treated hypertension
What is an ASA grade 3?
Severe systemic disease imposing functional limitation on activity
What is an ASA grade 4?
Incapacitating systemic disease which is a constant threat to life eg unstable angina
What is an ASA grade 5?
Moribund patient unlikely to survive 24 hours with or without surgery
What pre-op investigations should be done for minor surgery?
U&Es in older people or ASA3+ if at risk of AKI
ECG if over 40 or ASA 3+
What pre-op investigations should be done for intermediate surgery?
FBC is renal or cardiovascular disease
U&Es if at risk of AKI
LFTs and clotting if liver disease or on anticoagulants
ECG if cardiovascular, renal disease, or diabetes or ASA3+
?ABG
What pre-op investigations should be done for major or complex surgery?
FBC U&Es Clotting and LFTs ECG in most people ?Cross match/group and save ?ABG
When is a group and save and when is a cross match done before surgery?
Group and save is if there maybe some blood loss but it is not routine for this procedure eg in appendicectomy
Cross match if blood loss is anticipated
Give 3 examples of minor surgery?
Release of peripheral nerve entrapment at the wrist
Tooth extraction
Excising skin lesion
Drainage of middle ear
Give 3 examples of intermediate surgery
TOnsillectomy
Excising varicose veins
Arthroscopy
ECT
Give 3 examples of major surgery
Total joint replacement Lung surgery THyroidectomy Organ transplantation Excision of colon
What are the body’s requirements for water and electrolytes?
30ml/kg/day of water
Roughly 1-2mmol/kg.day of sodium, potassium and chloride
50-100g per day of glucose
How is fluid resuscitation done?
500ml boluses in 15 mins of either Hartmann’s or normal saline, up to 2 litres as required
How does the composition of losses from vomit differ from plasma and what is the importance of this?
Has lower sodium and higher potassium and chloride. This means it puts pt at risk of hypochloraemic hypokalaemic alkalosis. This should be adjusted for in fluid management
How do fluid losses from sweating impact on fluid management decisions?
Sweat has relatively low electrolytes so can predispose to hypernatraemia. Be careful not to overload with sodium
How can post-op pain be minimised?
Pre-op counselling
Pre-emptive analgesia peri-operatively
Post-op analgesia
Name 3 methods of peri-operative pre-emptive analgesia?
IV long acting analgesia Local anaesthetic infiltration at wound edges Regional nerve blocks Epidural IV/suppository NSAID before waking
What monitoring should be done in a patient with an epidural?
Look out of severe hypotension and respiratory depression (signs of toxicity)
What are the benefits of PCA?
Excellent continuous pain relief
Minimal sedation
Minimal respiratory depression
Give 5 complications that may manifest as excessive post-op pain
Compartment syndrome Haematoma Infection DVT MI Acute limb ischaemia Haemorrhage Anastamotic leak Biliary leak Abscess Obstruction/ileus/constipation Urinary retention Bowel ischaemia #NOF if fall
How should mild-moderate post-op pain be managed?
Paracetamol
Cocodamol
Mild oral NSAID eg ibuprofen
How should moderate post-op pain be managed?
Paracetamol
Codeine/dihydrocodeine
Oral/suppository stronger NSAID eg diclofenac
How should moderate-severe post-op pain be managed?
Moderate opiate eg oxycodone or tramadol
IV NSAID eg diclofenac
Oral slow release morphine
PCA morphine/diamorphine
Give 5 causes of post-op shortness of breath
Acute bronchopneumonia Aspiration Lobar collapse Pneumothorax PE Atelectasis ARDS Abdominal distension Cardiac failure Hyperventilation
Give 5 conditions associated with the development of ARDS
Radiation pneumonitis Lung contusion Sepsis Severe acute pancreatitis Near-drowning Aspiration of gastric contents Inhalation of corrosive materials Fat, air, or amniotic fluid embolism Multiple trauma with shock Major head injury Massive blood transfusion DIC Eclampsia Cardiopulmonary bypass Severe allergic reactions Drug overdose
How does atelectasis occur?
Mucus is retained in the bronchi causing bronchial obstruction. Alveoli supplied by those bronchi collapse as air in them is reabsorbed
Collapse of lung segments with reduced ventilation
Secondary infection may occur
Give 3 patient factors increasing the risk of atelectasis
Obesity Pregnancy Smoker Muscular weakness Difficulty coughing
Give 3 treatment factors that increase the risk of developing atelectasis
Opiates Wound pain NG tube Irritant anaesthetic drugs Atropine
Give 5 features of atelectasis
Dyspnoea Tachycardia Pyrexia Cyanosis Painful cough Reduced chest expansion Basal dullness Reduced air entry Crepitations
How does atelectasis appear on an x ray?
Opacity
How is atelectasis managed?
Extensive chest physiotherapy
Ensure adequate analgesia to aid mucus clearance
Treat any secondary infection
What is acute respiratory distress syndrome?
Interstitial oedema and reduced ling compliance as a result of a lung injury. Causes large VQ mismatch and respiratory failure
How does ARDS occur?
Insult to lung raises the pulmonary capillary permeability, causing exudate of fluid into alveolar interstitium causng interstitial oedema and reduced lung compliance and so reduced ventilation
Damage to alveolar cells also causes alveolar spaces to fill with fluid
There is a VQ mismatch causing a large shunt
On recovery, there is interstitial fibrosis
What are the clinical features of ARDS?
Rapid, shallow breathing
Scattered crepitations
Reduced PO2
What is the appearance of ARDS on chest x ray?
Progresses from normal to increase in interstitial markings to white out
How is ARDS managed?
ICU bed Ventilation with PEEP Monitor right atrial pressure TOE to monitor cardiac output Loop diuretics or haemofiltration to maintain negative fluid balance
Give 5 causes of post-op tachycardia
Anxiety Pain Atrial fibrillation Atrial flutter Infection Circulatory disturbance Thyrotoxicosis Hypovolaemic shock Haemorrhage Dehydration Cardiac failure MI Anastamotic leak
Give 5 causes of post-op pyrexia
Drug reaction Transfusion reaction Thyrotoxic crisis Phaeochromocytoma Malignant hyperthermia Malaria Central or peripheral line infection UTI Wound infection Pneumonia PE Haematoma Anastamotic leak DVT
What drugs commonly cause PONV?
Opiates
Erythromycin
Metronidazole
Give three causes of immediate PONV
Anxiety Gut handling Vestibular stimulation Oropharyngeal stimulation Hypotension Hypoxia Pain
What features of PONV may indicate bowel obstruction?
If there’s sustained vomiting more than 2 days post-op
What are the two main causes of post-op oliguria?
Urinary retention
Reduced urinary production
Give 3 causes of post-op urinary retention
Pre-existing outlet obstruction
Difficulty with passing urine supine
Difficulty passing urine without privacy
Overfilling of bladder due to accumulation of large urine volume during operation
Transient disturbance of neurological control
Wound pain inhibiting abdominal muscle contraction
Specific surgery predisposing to retention
Constipation
Which surgeries increase the risk of post-op urinary retention?
Abdominoperineal rectal resection
Bilateral inguinal hernia repair
How is post-op urinary retention managed conservatively?
Adequate analgesia
Encourage mobility to be able to use commode/bottle or wheel to bathroom and give time alone
Encourage bowel movements
How is post-op oliguria managed?
Conservatively
Catheterisation
Flush catheter if already in situ
What examination findings suggest urinary obstruction?
Palpable suprapubic mass
Dull to percussion
What are the common causes of reduced post-op urine production?
Reduced renal perfusion due to hypovolaemia
Hypotension
Cardiac failure
MI
How is reduced post op urine production managed?
Catheterisation to monitor output
Fluid challenge if cause thought to be hypovolaemia
What are the two types of neuromuscular blockers?
Depolarising
Non-depolarising
Give an example of a depolarising neuromuscular blocker and explain its action
Suxamethonium
Causes depolarisation and then blocks repolarisation causing paralysis until is hydrolysed by cholinesterase
When is suxamethonium used?
RSI
Urgent tracheal intubation, esp if at high risk of aspiration
Give 3 side effects of suxamethonium
Limb girdle pain
Malignant hyperpyrexia
Prolonged apnoea if deficient in (pseudo)cholinesterase
Raised intraocular pressure
Histamine release
Rise in potassium. Can be large in eg burns, crush injuries
Give an example of a non-depolarising neuromuscular blocker and explain its action
Atracurium
Blocks ACh’s access to nicotinic receptors so cannot cause depolarisation
When are non-depolarising neuromuscular blockers used?
Non-urgent tracheal intubation
Maintenance of muscle relaxation after suxamethonium
How is neuromuscular blockade reversed?
By giving anticholinesterase eg neostigmine
Name 3 IV anaesthetic agents
Propofol
Etomidate
Sodium thiopentone
Ketamine
What are the main benefits of propofol?
Rapid acting
Rapidly wears off
Metabolites don’t accumulate so can be used for maintenance
Give 3 side effects of propofol
Involuntary movements Reduced cerebral blood flow Myocardial depression Pain on injection Hypotension Ventilatory depression
When is sodium thiopentone used?
For rapid sequence induction
What are the disadvantages of sodium thiopentone?
Causes significant myocardial depression
Rapidly accumulates so can’t be used for maintenance
Which IV anaesthetic agents are safe in cardiovascular instability?
Etomidate
Ketamine
What is a major side effect of etomidate?
Adrenal suppression
Name three factors that increase MAC
Children Chronic alcohol use Chronic opioid use Hyperthermia Hyperthyroidim Hypernatraemia Raised catecholamines
Name three factors that reduce MAC
Old age or neonates Hypothermia Hypothyroidism Hyponatraemia Acute alcohol use Acute TCA use Acute opioid use Acute benzodiazepine use Pregnancy Anaemia Lithium
Name two inhaled anaesthetic agents
Isoflurane
Desflurane
Sevoflurane
Which inhaled anaesthetic agents allow rapid changes in depth of anaesthesia and why is this??
Desflurane
Sevoflurane
Have low solubility so changes in concentration rapidly change the depth and affect on brain
What is the benefit of adding adrenaline to a local anaesthetic?
Cause vasoconstriction reducing rate of absoprtion, reducing toxicity and increasing duration of action
What is the difference between APTT and PT?
APTT measures intrinsic pathway (9, 11, 12 and 10)
PT measures extrinsic pathway (1, 2, 7, 5, 10)
What is the action of heparin?
Activates antithrombin 3 to break down clots
How is the action of heparin reversed?
Protamine sulphate
What are the side effects of heparin?
Bleeding
Osteoporosis
Hyperkalaemia
Thrombocytopenia
How is heparin monitored?
Unfractionated monitored with APTT
What is the action of warfarin?
Inhibitis vitamin k so reduces levels of vit K dependent factors (10, 9, 7, 2) and protein C
Give 3 side effects of warfarin
Purple toes
Skin necrosis
Haemorrhage
Teratogenesis
What is the thromboprophylaxis regime for general surgery patients?
5000 units sc dalteparin night before surgery or intra-operatively
Below knee AES
Intermittent pneumatic compression boots in theatre
What is the thromboprophylaxis regime for vascular surgery patients?
5000 units sc dalteparin night before surgery or intraoperatively unless undergoing neck surgery, eg CEA
Intermittent pneumatic compression stockings on individual basis
What is the thromboprophylaxis regime for endocrine surgery patients?
Below knee AES
Name 3 contraindications to the use of LMWH
Recent cerebral haemorrhage
Haemophilia
Severe hypertension
Acute bacterial endocarditis
Give 3 contraindications to the use of anti-embolic stockings
Peripheral arterial disease Peripheral neuropathy Fragile skin Cardiac failure Pulmonary oedema secondary to congestive heart failure Severe leg oedema
Name 3 benefits of surgical antibiotic prophylaxis
Reduces incidence of surgical site infections
Minimises affect on patients host defences
Reduces adverse effects
Reduces effects on patient’s normal bacterial flora
What antibiotic prophylaxis is used in vascular surgery?
3 doses of co-amoxiclav or teicoplanin and gentamicin
What antibiotic prophylaxis is given in abdominal surgery?
If upper GI, coamoxiclav or teicoplanin + gentamicin
If lower, metronidazole +/- gentamicin
Name two operations that are particularly at risk of post-op haemorrhage
THyroidectomy
Parathyroidectomy
Angiography
Laparoscopic surgery with pfannenstiel incision
What is the cause of reactive post-op bleeding?
Usually bleeding from a slipped ligature or a vessel that was missed due to hypotension induced vasoconstriction. Bleeding will only occur once BP normalises
What is the main cause of secondary post-op bleeding?
Erosion of a vessel due to a spreading infection
What are the 3 peak times of operative haemorrhage?
Primary occurs intraoperatively
Reactive occurs within 24 hours
Secondary usually occurs after 7-10 days
What is the difference between a provoked and an unprovoked VTE?
Provoked VTEs are associated with a transient risk factor that can easily be removed
Unprovoked VTEs occur in the absence of a transient risk factor so there may either be no risk factor or there may be one that is persistent and not easily correctable eg cancer
What are the clinical features of a DVT?
Swelling and pain in the leg
Altered skin colour and temperature
Vein distension
Tenderness
What advice should be given to the patient after a DVT has resolved?
To increase walking exercise
To keep leg elevated whilst sitting
What is post-thrombotic syndrome of the leg?
A complication of a DVT with chronic venous hypertension, leading to pain, swelling, dermatitis, hyperpigmentation, ulceration and lipodermatosclerosis
